Compact roof-covering system

ABSTRACT

A covering system for roofs and for the outside of building walls is provided in which, on top, a high range of various decorative materials and elements can be fixed without penetrating the watertight layer. The system contains protruding elements connected to the support and flexible watertight membranes arranged so as to cover and contact essentially the complete support surface, including the protruding elements. Panels, preferably rigid insulation panels with excellent resistance to water, are arranged so as to hold down the watertight membranes onto the support, thus protecting the membrane from thermal cycling, UV rays and physical damage. The panels can be fixed with non-penetrating fastening means to secure the complete system to the protruding elements and to the support.

FIELD

The invention relates to watertight roof constructions of the invertedroof type. Most traditional sloped roofs are constructed with amultifunctional outer surface layer, the covering. For such roofs, thecovering materials provide for a watertight surface and also ensure to acertain degree a decorative function. The combination of requirementsresults in restrictions in the choice of cover materials, arrangement ofcover elements, roof shapes and slopes.

BACKGROUND

In traditional roofs, two common alternatives are known: the double skinroof and the inverted roof. In FR 2713687, U.S. Pat. Nos. 3,411,256 and3,763,614 illustrations are given of double skin and inverted roofs.

Double skin roofs consist essentially of a support, an insulation layer,a watertight membrane, a secondary support and a decorative layer. Sincein such a system the watertight membrane is hidden, it is difficult, incase of water leaks, to localize the infiltration and to repair it.Notwithstanding this, most double skin systems use penetrating fixings,thus increasing the risk for water leaks. Another disadvantage of thesystem is caused by the penetrating fixings, which form thermal bridgesand increase the internal condensation risk. Internal condensation has adeleterious effect on the life of the roof. Reducing the number offixings has consequences towards the dimensions of the fixings, possiblycausing larger thermal bridges. Other disadvantages are the fact thatthe decorative layer always needs a secondary metal support and the factthat double skin roofs mostly are characterized by a thick build-up oflayers.

The inverted roof, also known as upside down roof, was initiallydeveloped for flat roof construction. In general, insulation can beincorporated into a flat roof construction, either over or under thewatertight membrane of the roof. Where the insulation system is placedon top of the watertight membrane, this is usually referred to as aninverted roof. Such a roof protects the watertight membrane from thermalcycling, effects of UV rays, weathering and physical damage. In aconventional inverted roof, the insulation is provided by foamed slabs,which are placed on top of the watertight membrane. To prevent the slabsof being blown away, or floated off, it is necessary to anchor them inplace. In general, it is not possible to use mechanical fixings sincesuch fixings normally would penetrate the watertight membrane, causingleaks. Conventionally, the insulation slabs are laid loosely on top ofthe watertight membrane on a flat roof; ballast with gravel or pavingslabs are further added, for an additional loading of at least 50 kg/m².This type of construction certainly cannot be described as lightweight.Also, the use of such a conventional inverted roof is restricted to lowroof slopes: due to the absence of fixings, there is no resistanceagainst sliding of the insulation and of the ballast layer.

SUMMARY

The present invention addresses the problem of providing a roofconstruction that minimizes the risk of water leaks, that has a compactbuild-up, that retains the advantages of the inverted roof and thatstill allows for the use of a broad range of decorative elements andmaterials. The invention also addresses the problem of providingsimplicity of installation with a mid number of parts, and the need tokeep the installation inexpensive by minimizing labor cost. Theinvention can be used for all roof slopes between 0° and 90°. This meansthat vertical parts, such as building walls, and horizontal parts, suchas flat roofs and gutters, can be covered with the invented system. Theinvention is particularly interesting for roofs with a slope larger than0° and smaller than 90°.

According to the invention, there is provided an inverted roofcomprising

-   -   a support, defining the surface to be covered;    -   one or more protruding elements connected to the support;    -   one or more flexible watertight membranes arranged so as to        cover and contact essentially the complete surface to be        covered, and covering the protruding elements; and    -   one or more panels of thermal insulating material;        where the panels press the watertight membranes against the        support, and are secured to the protruding elements by fastening        means. In one particular embodiment, to hold down the membranes,        the panels cover and contact essentially the complete surface of        the watertight membranes.

The support can be a wood deck, a layer of concrete or a steel frame.The protruding elements preferably consist of linear members connectedalong their longest dimension to the support in a direction parallel tothe expected water flow. This configuration avoids water build-up andstagnation alongside these linear members. Protruding elements may alsoconsist of punctual members, or a combination of linear and punctualmembers. The use of linear members offers some benefits towards thewatertight membranes, as illustrated below, but special attention isneeded to avoid water stagnation behind them. The use of punctualmembers does not require this attention, but needs special prefabricatedwatertight membranes.

One or more flexible watertight membranes are placed over the protrudingelements and the support. The watertight membranes may consist ofstrips, sheets or special prefabricated sheets. In this text, strips areunderstood as being oblong membranes, typically available on reels.Sheets are understood as large-surface covering membranes, directlyproduced as such or consisting of several strips, pre-assembled in theworkshop. Special prefabricated sheets are described as membranes withprotuberances, pre-formed in the workshop. The watertight membranes canbe placed without bonding adhesives onto the support. This keeps theinstallation inexpensive by minimising labour costs and facilitates theseparate recycling of all materials used.

When linear protruding elements are used, it is possible to use two ormore watertight membranes in the form of adjacent strips. The overlapsof the watertight membranes are preferably situated on the linearprotruding members, thus forming standing seams. Overlaps with standingseam are easier to execute and are less critical towards waterinfiltration than conventional overlaps. Standing seams need fewerefforts than conventional overlaps for an equal or even higher watersealing quality.

When punctual protruding elements are used, special prefabricated sheetswith pre-assembled protuberances are arranged so that each protuberancefits exactly over each punctual protruding element. When a combinationof linear and punctual protruding elements is chosen, the use ofprefabricated sheets can be combined with the use of standing seams.

The flexible watertight membranes preferably consist of a syntheticmaterial with a primary watertight function such as EPDM rubber(Ethylene Propylene Diene Methylene Terpolymer), PVC (polyvinylchloride), or CPE (chlorinated polyethylene). They may also consist ofnon-UV resistant watertight material Such as PE (polyethylene). Amembrane thickness of less than 0.8 mm is advantageous as thisfacilitates its placement while being lighter and cheaper.

Onto the protruding elements and watertight membranes, panels are posed.The fastening mean protect the panels from wind uplift, water uplift andsliding. The fastening weans preferably do not penetrate the watertightmembranes, since this always creates an extra risk for water leaks. Whenpenetrating fastening means are used, they need special attention topreserve the water sealing function. This can be achieved by usingrelatively high protruding elements, allowing to position thepenetration holes 4-10 cm above the plane defined by the watertightmembranes. Depending upon the type of the panels, different fasteningmeans can be used.

The panels covering the watertight membranes consist of thermalinsulating material such as extruded (XPS) or expanded (EPS)polystyrene, cellular glass or Mineral wool board. This way, the panelsprotect the watertight membranes from uplift, thermal cycling, UV raysand physical damage.

The fastening means securing the panels to the protruding elementsadvantageously consist of synthetic material, preferably with a thermalconductivity of less than 0.4 W/m/K. This avoids the formation of coldbridges.

When using panels with relative high pull-off resistance Such as XPS, inparticular XPS panels coated with a UV resistant layer, they can berelied upon as a basis to affix other structures, for instancedecorative elements connected to the XPS panels by screws.

Panels with relative low pull-off resistance, such as water and weatherresistant mineral wool or EPS, are preferably covered with one ore moresections of wire net, which can be secured to the protruding elements.The wire net preferably consists of woven metal wire. The decorativestructures can be affixed to this wire net.

The decorative structures are preferably fixed without penetrating thewatertight membranes. This outer structure only has an aestheticfunction, the water sealing function being ensured by the watertightmembranes. Decorative elements made out of unconventional materials canbe used, as the joints between the elements do not need to bewatertight.

Glue or any other type of adhesive material can be applied to help infixing the membranes to the support, the overlapping membranes to eachother or the panels to the watertight membranes. An adhesive-free designis however preferred.

The present invention is characterised by freedom of choice. All of thefollowing items can be combined:

-   -   different kinds of base supports: wood, metal or concrete;    -   linear or punctual protruding elements;    -   flexible watertight membranes in the shape of strips, sheets or        specially prefabricated sheets;    -   water and weather resistant panels with high pull-off resistance        or not;    -   decorative material fixed with use of spacers, with use of a        secondary metal work, with direct fixation onto the protruding        elements or with direct fixation onto the panels or net.

DETAILED DESCRIPTION

Several embodiments of the invention will now be described by way ofexample, with reference to the drawings.

FIG. 1 shows a transversal section of a concrete deck with linearprotruding elements. The watertight membranes consist of strips withdouble overlaps and standing seam. Over the water and weather resistantinsulation, a net is connected to the protruding elements withoutpenetrating the watertight membranes. The decorative material is fixedonto the net.

FIG. 2 shows a transversal section of a concrete deck with linearprotruding elements. The watertight membranes consist of a sheetoverlapping the protruding elements. The water and weather resistantinsulation is connected to the protruding elements without penetratingthe watertight membrane. The decorative material is fixed directly intothe rigid insulation material.

FIG. 3 shows a transversal section of a wood deck with punctualprotruding elements. The watertight membrane consists of specialprefabricated sheets encapsulating the protruding elements. The waterand weather resistant insulation is connected to the protruding elementswithout penetrating the watertight membrane. The decorative material isfixed onto a secondary support fixed directly into the rigid insulationmaterial.

FIG. 4 shows a longitudinal section of a metal deck with a supplementarylayer and linear protruding elements perpendicular to the steel deckvalleys. The water and weather resistant insulation is connected to theprotruding elements without penetrating the watertight membrane.Likewise, the decorative material is fixed with direct connectors ontoto the protruding elements without penetrating the watertight membrane.

FIG. 5 details the fastening means ‘type A’ (16) shown in FIGS. 2, 3 and4.

FIG. 6 details the fastening means ‘type B’ (17) shown in FIG. 1.

FIG. 7 details the fastening clip (18) shown in FIG. 1.

FIG. 8 details the special screw (19), shown in FIGS. 2 and 3.

FIG. 9 details the linear protruding element (20) shown in FIGS. 1, 2and 4.

FIG. 10 details the punctual protruding element (21), shown in FIG. 3.

FIG. 11 details a direct connector (22) shown in FIG. 4.

For the base deck (1), also called the support, wood, steel and concretecan be used. FIGS. 1 and 2 show a concrete deck (1). FIG. 3 shows a wooddeck and FIG. 4 a metal deck (1). All deck constructions have beenchosen by way of illustration and are usable in any combination. Whenusing a metal deck, as shown in FIG. 4, a supplementary layer (2) isneeded to offer a continuous supporting surface. This layer can bemetal, plywood or insulation material, and can be loose laid.

On the base deck (1) or on the supplementary layer (2), linearprotruding elements (20) or punctual protruding elements (21) aremechanically connected. Such type of elements can be also found in U.S.Pat. Nos. 4,744,187 and 4,833,853.

Linear protruding elements (20) can be L- or U-shaped profiles with aheight and a base of about 3-10 cm. A partially closed U-shape, allowingfor the insertion and retention of the head of suitably shaped boltsused for securing the panels, is well adapted: it results in astructurally stable system while any penetration of the watertightmembrane is avoided. The dimensions of the linear protruding elements,their axial distance and the number of fixations into the deck arefunction of the expected physical forces and of the properties of allmaterials utilised. Typically, the height of the linear protrudingelements will be around 4 cm. The linear protruding elements are placedin-line, maintaining gaps of about 2-5 mm between co-linear elements.Normally, an axial distance of 40-120 cm is used. However, particularroof shapes can be executed by following upwardly convergent lines.

Punctual protruding elements (21) can be short L-shaped profiles with aheight and a base of 3-10 cm. The dimensions of the punctual protrudingelements, their two dimensional axial distance and the number offixations into the deck, are function of the expected physical forcesand of the properties of all materials utilised. Typically, the heightof the linear protruding elements will be around 4 cm. Due to theirlimited length, their positioning is not critical in view of the waterflow. The protruding elements can be placed according to a regularpattern, with an axial distance of 40-120 cm.

Any combination of linear and punctual protruding elements can also beenvisaged.

Flexible watertight-membranes consisting of strips (3), sheets (4) orspecial prefabricated sheets (5) ensure the water sealing function ofthe roof. The material of the watertight membranes can be EPDM rubber,PVC or other. The watertight membranes can be loose laid or bonded ontothe base deck (1, 2).

When linear protruding elements (20) are used, the longitudinal overlapsof the watertight membranes (as in 3) are preferably situated on thelinear protruding elements, thus forming standing seams with doubleoverlap, as in FIG. 1. Provided that the height of the standing seam issufficient and that capillarity is avoided, the overlaps can even bemade watertight without any sealer.

Horizontal overlaps can also be accepted (as in 5), although they createa higher leak risk than standing seams. Transversal horizontal overlapscan be avoided by using long watertight membranes from gutter to hip.Horizontal overlaps of the watertight membranes can be made watertightwith the traditional treatment and techniques developed by themanufacturers of the membranes, such as fohning, seaming or sealing.

The wind uplift resistance of the watertight membranes (3,4,5) isensured by the particular positioning of the insulation panels (6, 7).The insulation panels have to be rigid, waterproof and weatherproof, andmay provide excellent thermal insulation. If directly subjected to UVrays, the insulation panels should be resistant by themselves orprotected by a special coating. For XPS, the panels should be protectedon top by an external thin armature coated with a thin UV resistantlayer.

For this invention the panels can be divided into two groups:

-   -   water- and weatherproof insulation with enough reliable pull-off        resistance (6) such as e.g. XPS as illustrated in FIGS. 2, 3 and        4;    -   water- and weatherproof insulation without enough reliable        pull-off resistance (7) such as e.g. certain types of mineral        wool and certain types of EPS (expanded polystyrene), as        illustrated in FIG. 1.

In both cases, the insulation panels cover the watertight membranescompletely, thus protecting them from UV rays, thermal cycling andphysical damage during execution and thereafter. This implies that theirthickness exceeds the height of the protruding elements. The insulationpanels preferably fully contact the watertight layer (3,4,5), preventingwind uplift. The insulation panels can be loose laid without use ofadhesives.

The water- and weatherproof insulation panels (6, 7) are mechanicallysecured to the protruding elements (20, 21) by fastening means ‘type A’(16) or ‘type B’ (17). FIGS. 2, 3 and 4 show water- and weatherproofinsulation with enough reliable pull-off resistance (6). In this case,the panels are directly connected onto the protruding elements (20, 21)by fastening means ‘type A’ (16), and fixed to the protruding elements,preferably without penetrating the watertight membranes. The fasteningmeans ‘type A’ are preferably made of stainless or galvanised steel andplaced at each joint of the insulation panels.

FIG. 1 shows water- and weatherproof insulation without enough reliablepull-off resistance (7). In this case, before placing the panels,fastening means ‘type B’ (17) are fixed to the protruding elements,preferably without penetrating the watertight membranes. Next, thepanels are posed between the fastening means ‘type B’ (17). The panelsare secured by posing a metal net (8) on top. The fastening means ‘typeB’ (17) are normally made of stainless steel or galvanised steel, theirquantity being chosen according to the expected climate and theproperties of the net. The net is mechanically connected to theprotruding fastening means ‘type B’ with fastening clips (18). The net(8) preferably consists of stainless steel wire with a thickness chosenaccording to the needed pull-off resistance. Net sections with a lengthof 100 cm and a width slightly larger than the axial distance of theprotruding elements are easy to handle and to fix, while resistantoverlaps are obtained.

The top layer can consist of all kinds of decorative elements: rigidpanels (13), small rigid elements (14) or blankets (15) made ofmaterials like wood, metal, plastic or even grass. The only restrictionis the weight and the expansion coefficient. If a net (8) is used, thedecorative elements can be fixed onto the net with traditional means (9)like clips, without penetrating the watertight membranes. An air gap canbe created with use of spacers (10) or with use of secondary metal work(12).

If a water- and weatherproof insulation with enough reliable pull-offresistance (6) is used, the decorative elements can be fixed onto theinsulation panels with special screws (19), without penetrating thewatertight membrane. An air gap can be created with use of spacers (10)or with use of secondary metal work (12). The decorative elements canalso be fixed without air gap (11). The special screws (19) co-operatewith the XPS panels so as to provide high pull-off resistance.

In a special embodiment, the decorative elements need to be fixeddirectly onto the protruding elements as shown in FIG. 4 with connectors(22) as in FIG. 11.

1. An inverted roof, comprising: a support, defining a surface to becovered; one or more protruding elements connected to the support; oneor more flexible watertight membranes arranged to cover and contactessentially the complete surface to be covered and to cover theprotruding elements; and one or more panels of thermal insulatingmaterial; wherein the panels press the watertight membranes against thesupport and are secured to the protruding elements by fastening meansand wherein the fastening means do not penetrate the one or morewatertight membranes.
 2. The inverted roof according to claim 1, whereinthe one or more panels cover and contact essentially the completesurface of the watertight membranes.
 3. The inverted roof according toclaim 1, wherein the one or more protruding elements are linear membershaving a longest dimension, the linear members being connected alongtheir longest dimension to the support in a direction parallel to waterflow.
 4. The inverted roof according to claim 3, wherein at least twowatertight membranes are shaped as adjacent strips having edges, theadjacent strips being arranged with their edges overlapping along thelinear members.
 5. The inverted roof according to claim 1, wherein theone or more watertight membranes consist of synthetic material.
 6. Theinverted roof according to claim 5, wherein the one or more watertightmembranes have a thickness of less than 0.8 mm.
 7. The inverted roofaccording to claim 1, wherein the thermal insulating material isextruded or expanded polystyrene, cellular glass, or mineral wool board.8. The inverted roof according to claim 7, wherein the extrudedpolystyrene panels are coated with a UV resistant layer.
 9. The invertedroof according to claim 7, wherein the extruded polystyrene panels areused as a basis to affix other structures.
 10. The inverted roofaccording to claim 9, wherein the other structures are connected to theextruded polystyrene panels by screws.
 11. The inverted roof accordingto claim 1, wherein the fastening means consist of synthetic material.12. The inverted roof according to claim 11, wherein the syntheticmaterial has a thermal conductivity of less than 0.4 W/m/K.